Vehicle battery mounting structure

ABSTRACT

A vehicle (1) comprises a passenger compartment (2) in which a front seat (32F), a rear seat (32R), and a floor (33) between the front seat (32F) and the rear seat (38R) are provided. A first group (S1) of batteries (3) is mounted under the front seat (32F), a second group (S2) of the batteries (3) is mounted under the floor (33), and a third group (S3) of the batteries (3) is mounted under a rear seat (32R). By setting a height (h2) of the second group (S2) of the batteries (3) to be lower than respective heights (h1, h3) of the first and third groups (S1, S3) of the batteries (3), a battery mounting capacity of the vehicle (1) can be increased without affecting the comfort of the passenger compartment (2).

FIELD OF THE INVENTION

This invention relates to a layout of batteries mounted on a vehicle.

BACKGROUND OF THE INVENTION

Japanese Patent Serial No. 3199296, issued by The Japan Patent Office in2001, teaches placing a number of the batteries side by side under afloor panel of a vehicle so as to mount as many batteries as possible onthe vehicle.

The batteries are arranged on a plain surface in a vehicle transversedirection and a vehicle longitudinal direction closely to form a batterygroup. A front seat and a rear seat are provided in a passengercompartment of the vehicle and the battery group is located under afloor panel of the passenger compartment including regions for the frontseat and the rear seat.

SUMMARY OF THE INVENTION

In the prior art battery mounting structure described above, thebatteries are arranged on a plain surface and have a uniform height. Inother words, if an increase in the battery mounting capacity of thevehicle is required, the floor panel must be raised, and as a result,the comfort of the passenger compartment is impaired. Specifically, whenthe floor panel between the front seat and the rear seat is raised, thefoot position of passengers sitting in the rear seat is raised and thepassengers may feel discomfort.

According to the prior art battery mounting structure, it is oftendifficult to satisfy a requirement relating to the comfort of thepassenger compartment of a vehicle together with a requirement relatingto the battery mounting capacity of the vehicle.

It is therefore an object of this invention to provide a batterymounting structure that can satisfy both of the above requirements.

To achieve the above object, this invention provides a vehicle batterymounting structure for mounting a plurality of batteries under a floorpanel of a vehicle, comprising a first group of the batteries, a secondgroup of the batteries disposed to the rear of the first group of thebatteries with respect to a vehicle longitudinal direction, and a thirdgroup of the batteries disposed to the rear of the second group of thebatteries with respect to the vehicle longitudinal direction. Herein, aheight of the second group of the batteries is set to be lower than aheight of the first group of the batteries and a height of the thirdgroup of the batteries, and the height of the third group of thebatteries is set to be higher than the height of the first group of thebatteries.

This invention also provides a battery case fixed in a vehicle foraccommodating a stack of batteries, comprising a first battery housingpart, a second battery housing part disposed to the rear of the firstbattery housing part with respect to a vehicle longitudinal direction,and a third battery housing part disposed to the rear of the secondbattery housing part with respect to the vehicle longitudinal direction.Herein, a height of the second battery housing part is set to be lowerthan a height of the first battery housing part and a height of thethird battery housing part, and the height of the third group of thebatteries is set to be higher than the height of the first group of thebatteries.

This invention also provides a battery mounting space formed in a floorpanel of a vehicle to face downward, comprising a first recess, a secondrecess formed to the rear of the first recess with respect to a vehiclelongitudinal direction, and a third recess formed to the rear of thesecond recess with respect to the vehicle longitudinal direction.Herein, a height of a bottom of the second recess is set to be lowerthan a height of a bottom of the first recess and a height of a bottomof the third recess, and the height of the third group of the batteriesis set to be higher than the height of the first group of the batteries.

This invention also provides a battery assembly fixed in a vehicle,comprising a first group of batteries, a second group of the batteriesdisposed to the rear of the first group of the batteries with respect toa vehicle longitudinal direction, and a third group of the batteriesdisposed to the rear of the second group of the batteries with respectto the vehicle longitudinal direction. Herein, a height of the secondgroup of the batteries is set to be lower than a height of the firstgroup of the batteries and a height of the third group of the batteries,and the height of the third group of the batteries is set to be higherthan the height of the first group of the batteries.

The details as well as other features and advantages of this inventionare set forth in the remainder of the specification and are shown in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of essential parts of a vehicleshowing a vehicle battery mounting structure according to thisinvention.

FIG. 2 is a horizontal sectional view of essential parts of the vehicleshowing the vehicle battery mounting structure.

FIG. 3 is a cross-sectional view of essential parts of the vehicle takenalong a line III-III of FIG. 2.

FIG. 4 is a plan view of a battery assembly according to this invention.

FIG. 5 is a perspective view of the battery assembly.

FIG. 6 is a perspective view of a battery mounting frame according tothis invention.

FIG. 7 is an exploded perspective view of a vertical battery stackaccording to this invention during a battery stacking process.

FIG. 8 is an exploded perspective view of a transverse battery stackaccording to this invention during a battery stacking process.

FIG. 9 is a perspective view of a case which accommodates the batteryassembly.

FIG. 10 is an electric circuit diagram of the battery assembly.

FIG. 11 shows an enlarged longitudinal sectional view of the case and abattery mounting recess according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 of the drawings, a vehicle 1 comprises a passengercompartment 2 and a front compartment 11 provided in front of thepassenger compartment 2. An arrow UP in the figure points verticallyupward and an arrow FR in the figure points frontward with respect torunning directions of the vehicle 1. The vehicle 1 is a so-calledelectric vehicle which runs under a motive force of an electric motor 12housed in the front compartment 11. The vehicle 1 may be a hybrid-drivevehicle which runs under a motive force generated by an electric motorand a motive force generated by an internal combustion engine or a fuelcell vehicle which runs under a motive force generated by an electricmotor that is driven by electric power generated by fuel cells.

To drive the electric motor 12, a number of batteries 3 are arranged inan under floor space of the passenger compartment 2 of the vehicle 1.

Referring to FIGS. 2 and 3, a pair of parallel side members 4 extendingin a vehicle longitudinal direction are provided under a floor panel 16forming a floor of the passenger compartment 2 of the vehicle 1. Anarrow WD in the figures points rightward in a vehicle transversedirection when facing frontward with respect to the running directionsof the vehicle 1. Front ends of the pair of side members 4 are fixed toa cross member 6 extending in the vehicle transverse direction of thevehicle 1. A pair of rear side members 9 are fixed to rear ends of thepair of side members 4. Rear ends of the pair of rear side members 9 arefixed to a rear cross member 10 extending in the vehicle transversedirection of the vehicle 1.

Both ends of the cross member 6 and both ends of the rear cross member10 are fixed to a side sill 7 which delimits a lower end of a dooropening serving as a part of a vehicle body. The pair of side members 4are located on the inner side of the side sill 7 and each of the sidemembers 4 is fixed to the side sill 7 via three outriggers 8. In FIGS. 2and 3, a part designated by a reference number 7 corresponds to an innerwall face of the side sill 7. The members 4, 6, 9, and 10 are disposedin advance under the floor panel 16 as a part of the vehicle body.

Referring again to FIG. 1, an electric motor 12 serving as a motiveforce source for vehicle running, and a battery charger 13 and aninverter 14 serving as related devices are housed in the frontcompartment 11 of the vehicle 1. The battery charger 13 is a device forcharging the batteries 3. The inverter 14 is a device for controllingcharge/discharge of the batteries 3. In the following description, theelectric motor 12 and the related devices will be referred tocomprehensively as electric equipment.

Referring to FIGS. 4 and 5, the batteries 3 are stacked in advance as abattery assembly 22 on the inner side of a battery mounting frame 21having a rectangular planar shape. The battery assembly 22 is thenfitted into a space surrounded by the pair of side members 4, the crossmember 6, the pair of rear side members 9, and the rear cross member 10from a lower side.

Referring to FIG. 6, the battery mounting frame 21 comprises arectangular frame 23 and a reinforcing member 24 which is arranged inthe rectangular frame 23.

The rectangular frame 23 comprises a front edge member 23 f, a rear edgemember 23 r, and a pair of side edge members 23 s which connect bothends of the front edge member 23 f and both ends of the rear edge member23 r. The front edge member 23 f, the rear edge member 23 r, and thepair of side edge members 23 s form four sides of a rectangle. It shouldbe noted that the terms front-aft or front end/rear end used in thedescription of the battery assembly 22 mean front-aft and front end/rearend in a state where the battery assembly 22 is fixed to the vehiclebody.

Each of the front edge members 23 f, the rear edge members 23 r, and thepair of side edge members 23 s is constituted by an upright wall portion28 and a flange portion 29 extending horizontally from a lower end ofthe upright wall portion 28, thereby providing the members 23 f, 23 rand 23 s with an inverted T-shaped cross-section.

The reinforcing member 24 comprises a girder 24 w fixed in therectangular frame 23 in the vehicle transverse direction, and a beam 24c connecting a middle part of the girder 24 w and a middle part of thefront edge member 23 f. The reinforcing member 24 is integrated into thebattery mounting frame 21 in advance by welding the girder 24 w and thebeam 24 c into a T-shape, and welding each end of the resultant T-shapemember to the rectangular frame 23.

According to the above structure, the inner space of the batterymounting frame 21 is divided into a front rectangular region in front ofthe girder 24 w and a rear rectangular region 26R to the rear of thesame. The front rectangular region is further divided into two frontrectangular regions 26F, 26F by the beam 24 c. A total area of the twofront rectangular regions 26F, 26F is substantially the same as an areaof the rear rectangular region 26R. The planar shape of theserectangular regions 26F, 26F, 26R is designed such that a long side ofthe rectangle is substantially double the size of a short side of therectangle.

Referring to FIG. 7, each battery 3 is formed into a flat cuboid. Thebatteries 3 are stacked in a direction of a shortest side of the threesides of the cuboid. In the following description, the other two sidesare referred to as a long side and a short side depending on a length ofthe sides.

In the two front rectangular regions 26F, 26F, the batteries 3 arestacked in the vertical direction in a state where the long side of thebatteries 3 is oriented in the vehicle transverse direction and theshort side of the batteries 3 is oriented in the vehicle longitudinaldirection. In each of the front rectangular regions 26F, four stacks ofthe batteries 3 are arranged in the vehicle longitudinal direction. Thenumbers of stacked batteries 3 are not constant. In the frontmost twostacks in the region 26F, four batteries 3 are stacked in each stackwhile in the rearmost two stacks in the region 26F, two batteries 3 arestacked in each stack. Thus twelve batteries are stacked in each of therectangular regions 26F, 26F.

In each stack in the front rectangular regions 26F, 26F, the batteries 3are stacked via spacers 37 b and strip-form plates 37 a. The spacer 37 bis a member comprising a columnar member and a large diameter partformed in the middle of the columnar member via a step on either side.Through-holes are formed through four corners of the batteries 3 inadvance so as to accommodate the columnar part of the spacer 37 b.Through-holes are also formed in the strip-form plates 37 a.

When the batteries 3 are stacked, one of the columnar parts of a spacer37 b is inserted into a through-hole of the battery 3 after passingthrough a through-hole of a strip-form plate 37 a, and the othercolumnar part of the spacer 37 b is inserted into a through-hole of anadjacent battery 3 after passing through a through-hole of a differentstrip-form plate 37 a. In this way, the large diameter part of thespacer 37 b is gripped between the two batteries 3 via the strip-formplates 37 a such that a stacking clearance of the batteries 3 is keptconstant. The strip-form plate 37 a and a spacer 37 c comprising acolumnar member and a large diameter part formed at an end of thecolumnar part via a step is attached to an uppermost battery 3 and alowermost battery 3.

Although not shown in the figures, a through-hole is formed axially ineach of the spacers 37 b and 37 c in advance. After stacking apredetermined number of the batteries 3, a pin is caused to penetratethe through-holes of the spacers 37 b and 37 c and a nut is screwed oneach end of the pin. The batteries 3 are thus integrated into a batterystack.

Referring to FIG. 4, a space G is provided between the stacks in one ofthe front rectangular regions 26F, 26F and the stacks in the other ofthe front rectangular regions 26_F, 26F. The space G is located abovethe beam 24 c and a region adjacent to the beam 24. The batteries 3 arestacked in the front rectangular regions 26F, 26F such that a terminal 3a of each battery 3 projects into the space G. The terminals 3 a of thebatteries 3, a harness 34 which electrically connects the terminals 3 aand the electric equipment in the front compartment 11, and a switch box35 and a junction box 36 interposed in the harness 34 are accommodatedin the space G.

Referring to FIG. 8, twenty-four batteries 3 are stacked in thetransverse direction of the vehicle in the rear rectangular region 26Rin a state where the long side of the battery 3 is oriented in thevehicle longitudinal direction. The batteries 3 are stacked withconstant clearances via the spacers 37 b such that the terminals 3 aproject frontward. An end plate 37 e is stacked on either end of thestack.

Although not shown in the figures, a through-hole is formed axially ineach of the spacers 37 b in advance. After stacking a predeterminednumber of the batteries 3, a pin is caused to penetrate thethrough-holes of the spacers 37 b and a nut is screwed on each end ofthe pin. The batteries 3 are thus integrated into a battery stack.

A supporting plate 37 d extending in the vehicle transverse direction isfixed to a front side face and a rear side face of the stack by screws37 f. Only one stack thus constructed is provided in the rearrectangular region 26R.

Referring to FIG. 5, according to the above layout of the batteries 3, agroup S1 of the batteries 3 comprising two stacks of four batteries 3stacked in the vertical direction and a group S2 of the batteries 3comprising two stacks of two batteries 3 stacked in the verticaldirection are provided in each of the two front rectangular regions 26F,26F in the battery mounting frame 21. A group S3 of the batteries 3comprising twenty-four batteries 3 stacked in the vehicle transversedirection is provided in the rear rectangular region 26R in the batterymounting frame 21. With respect to the stacking direction, the groups S1and S2 constitute a first battery unit 38F being a set of verticallystacked batteries 3 while the group S3 constitute a second battery unit38R being a set of transversely stacked batteries 3.

Referring to FIGS. 3 and 9, a case 22 a is fixed to the battery mountingframe 21 so as to accommodate the battery assembly 22.

The stacks of the batteries 3 are fixed to the case 22 a by screws, forexample. It is also possible to use the flange portion 29 extendinginward from the upright wall portion 28 to fix the stacks. The case 22 ais formed into a shape adapted to the battery assembly 22 in advance soas to prevent the stacks from displacing in the transverse,longitudinal, and vertical directions. It is preferable to form anopening or openings in a bottom of the case 22 a to increase a coolingcapability of the batteries 3. The shape and the number of the openingsmay be determined arbitrarily.

Referring to FIG. 8, it is preferable to accommodate a control unit 45constituted, for example, by a microcomputer to control the devices inthe junction box 36 in the case 22 a on one side of one of the endplates 37 e.

Herein, the battery mounting frame 21, the case 22 a, the stacks of thebatteries 3, the harness 34, the switch box 35, the junction box 36, andthe control unit 45 constitute the battery assembly 22.

Referring to FIGS. 1-4, the battery mounting frame 21 is fixed to thecross member 6, the pair of side members 4, the pair of rear sidemembers 9, and the rear cross member 10 using bolts penetrating theflange portion 29 that extends outward from the upright wall portion 28and nuts screwed onto the bolts. In the fixed state, the upright wallportion 28 of the front edge member 23 f faces the cross member 6, theupright wall portion 28 of the rear edge member 23 r faces the rearcross member 10, and the upright wall portion 28 of the pair of sideedge members 23 s faces the side members 4 and a part of the pair ofrear side members 9, respectively. Herein, the pair of side members 4,the cross member 6, the pair of rear side members 9, and the rear crossmember 10 constitute a fixed member for fixing the battery mountingframe 21 onto the vehicle body.

The battery mounting frame 21 fixed to the fixed member assists inincreasing the rigidity and strength of the vehicle body. Therectangular frame 23 and the reinforcing member 24 function as atransferring path for loads input during a vehicle collision.

A downward opening 30 shown in FIG. 3 is formed in the vehicle body bythe pair of side members 4, the cross member 6, the pair of rear sidemembers 9, and the rear cross member 10, which constitute the fixedmember. The space above the opening 30 is covered by the floor panel 16,thereby forming a housing recess 31 to accommodate the battery assembly22.

Mounting the battery assembly 22 on the vehicle body is performed byinserting the battery assembly 22 into the housing recess 31 from belowthe vehicle body and fixing the battery mounting frame 21 to the fixedmember using the bolts and nuts. By integrating a number of thebatteries 3 into the battery assembly 22 in advance, mounting thebatteries 3 on the vehicle 1 can be accomplished easily. The batteries 3thus mounted on the vehicle 1 can also be removed easily forreplacement.

As shown in FIG. 1, the vehicle 1 comprises a front seat 32F and a rearseat 32R in the passenger compartment 2. The shape and size of thebattery assembly 22, the shape and the size of the batteries 3, and thelocation of the fixed member are predetermined such that the group S1 ofthe batteries 3 is located substantially below the front seat 32F, thegroup S2 of the batteries 3 is located below the floor 33 between thefront seat 32F and the rear seat 32R, and the group S3 of the batteries3 is located below the rear seat 32R in a state where the batteryassembly 22 is fitted into the housing recess 31. Further, the shape ofthe floor panel 16 and the case 22 a are predetermined on the basis ofthe shape of the battery assembly 22.

Assuming that the height of the group S1 of the batteries 3 is h1, theheight of the group S2 of the batteries 3 is h2, and the height of thegroup S3 of the batteries 3 is h3, the relation h3>h1>h2 holds. Theheights h1 and h2 are common to the right rectangular region 26F and theleft rectangular region 26F.

The group S1 of the batteries 3 is located under the front seat 32F, andthe group S3 of the batteries 3 is located under the rear seat 32R. Bysetting the height h1 of the group S1 of the batteries 3 and the heighth3 of the group S3 of the batteries 3 to be greater than the height h2of the group S2 of the batteries 3, a space under the seats 32F and 32Rin the passenger compartment 2 can be utilized efficiently for mountingthe batteries 3, and a large number of the batteries 3 can be mounted onthe vehicle 1 without affecting the comfort of the passenger compartment2. Since the height h3 of the group S3 of the batteries 3 is higher thanthe height h1 of the group S1 of the batteries 3, the sitting level ofthe rear seat 32R becomes higher than the sitting level of the frontseat 32F in the passenger compartment 2. This setting is preferable interms of providing a wide view for passengers in the rear seat 32R.

The groups S1 of the batteries 3 on the right and left of the beam 24are constituted by sixteen batteries in total. The groups S2 of thebatteries 3 on the right and left of the beam 24 c are constituted byeight batteries in total. The group S3 of the batteries 3 is constitutedby twenty-four batteries. That is to say twenty-four batteries aremounted in front of the girder 24 w and in the rear of the girder 24 w,respectively. As a result, the weight of the group S3 of the batteries 3is heavier than the total weight of the groups S2 of the batteries 3 andheavier than the total weight of the groups S1 of the batteries 3, andsubstantially equal to the total weight of the groups S2 of thebatteries 3 and the groups S1 of the batteries 3.

According to the above arrangement of the batteries 3, the center ofgravity of the battery assembly 22 is located to the rear of the centerof a plan view of the battery assembly 22. Assuming that Cv in FIG. 4 isthe graphical center of the vehicle 1, the center of gravity of thebattery assembly 22 is located to the rear of the graphical center Cv ofthe vehicle 1. Considering that the electric equipment comprising theelectric motor 12, the battery charger 13, and the inverter 14 isaccommodated in the front compartment 11 of the vehicle 1, locating thecenter of gravity of the battery assembly 22 to the rear of thegraphical center Cv of the vehicle 1 is preferable in terms of theweight balance of the vehicle 1 in the front-aft direction.

In the groups S1 and S2 of the batteries 3, the batteries 3 are stackedsuch that the long side is oriented in the vehicle transverse directionand the short side is oriented in the vehicle longitudinal direction. Inthis case, the density of the batteries 3 or the clearance between thebatteries 3 in the vehicle transverse direction is determined accordingto the width W of the lower part of the vehicle body shown in FIG. 2 andthe length Wb of the long side of the batteries 3 shown in FIG. 4. Withrespect to the groups S1 and S2 of the batteries 3, a space G formedbetween a row of the battery stacks in one of the rectangular regions26F and a row of the battery stacks in the other rectangular region 26Fcontributes to this adjustment of the clearance. In the groups S1 and S2of the batteries 3, the batteries 3 are stacked in the verticaldirection. The respective heights h1 and h2 of the groups S1 and S2 ofthe batteries 3 can therefore be adjusted minutely by an adjustment unitequal to the length of the shortest side of the battery 3.

With respect to the group S3 of the batteries 3, the batteries 3 arestacked such that the shortest side is oriented in the vehicletransverse direction. Accordingly, by adjusting the stacking number ofthe batteries 3 and the clearance between the batteries 3 depending onthe width W of the lower part of the vehicle body, the length of thegroup S3 of the batteries 3 in the vehicle transverse direction can beadjusted minutely and a large number of the batteries 3 can be mountedusing the space under the rear seat 32R efficiently.

According to the type of the vehicle 1, a rear space in the passengercompartment 2 may be limited due to a rear wheel house 25 shown in FIG.2 or a rear suspension. Since the dimension in the vehicle transversedirection of the group S3 of the batteries 3, which is located in therear space in the passenger compartment 2, can be adjusted minutely asdescribed above, a difference in the size of the rear space in thepassenger compartment 2 can be absorbed easily.

As shown in FIG. 1, the groups S1 and S2 of the batteries 3 respectivelyhave two battery stacks arranged in the vehicle longitudinal direction.However, this number of battery stacks can be altered depending on thedimension of the vehicle 1 in the longitudinal direction. For example,the group S1 of the batteries 3 may be constituted by three batterystacks arranged in the vehicle longitudinal direction while the group S2of the batteries 3 is constituted by only one battery stack.

Thus, even when the layout of the seats of the vehicle 1 is changed, anoptimum layout of the batteries can be realized by simply altering thenumber of the battery stacks in the groups S1-S3 without modifying thedimensions of the battery mounting frame 21. As a result, the batterymounting frame 21 can be applied to various types of vehicles.

According to the battery mounting structure described above, the rearedge member 23 r and the girder 24 w of the battery mounting frame 21are located relatively near to the rear suspension. These members bringabout an effect of increasing the rigidity of the vehicle body against adirect load input into the vehicle body when a rear side of the vehicle1 undergoes a collision or an upward impact load transmitted from therear suspension to the vehicle body. In the group S3 of the batteries 3,by stacking the batteries 3 in close contact with one another andincreasing the strength of stack supporting members such as thesupporting plates 37 d, it is possible to cause the battery stack tocontribute to an increase in the rigidity and strength of the vehiclebody.

Since the harness 34, the switch box 35, and the junction box 36 areaccommodated in the space G and the groups S1 and S2 of the batteries 3are stacked such that the terminals 3 a project into the space G. Thespace G, which is not used for stacking the batteries 3, is utilizedeffectively in the layout of these members. Putting the first batteryunit 38F constituted by the vertically stacked batteries in front of thesecond battery unit 38R constituted by the transversely stackedbatteries is also preferable in terms of obtaining the space for thelayout of these members.

In the group S3 of the batteries 3, the batteries 3 are stacked suchthat the terminals 3 a project frontward, or in other words into theupper space of the girder 24 w. This layout of the batteries 3 ispreferable in terms of protecting the terminals 3 in case of collisionof the vehicle 1. Further, according to this layout of the batteries 3,connecting the harness 34 to the terminals 3 a can be performed easilyby using the upper space of the girder 24 w. Still further, thedurability of the harness 34 can be increased using the girder 24 w tosupport the harness 34.

Referring to FIG. 10, an electric circuit of the battery assembly 22will be described.

The electric circuit of the battery assembly 22 connects the batteries 3in the group S3 and the batteries 3 in the groups S1 and S2 on the rightand left rectangular regions 26F in series using the harness 34. Theswitch box 35 is interposed in the harness 34 between the batteries 3 inthe group S3 and the batteries 3 in the groups S1 and S2. The junctionbox 36 is interposed between the terminals connected to both ends of thebatteries 3.

The switch box 35 comprises a manually-operated relay 35 a and a fuse 35b connected in series. The manually-operated relay 35 a connects anddisconnects the group S3 of the batteries 3 and the groups S1 and S2 ofthe batteries 3. In this embodiment, the electric circuit of the batteryassembly 22 is divided into one circuit for the first battery unit 38Fconstituted by the groups S1 and S2 of the batteries 3 in the right andleft rectangular regions 26F and another circuit for the secondarybattery unit 38R constituted by the group S3 of the batteries 3. Theterminal voltage of the first battery unit 38F and the terminal voltageof the second battery unit 38R are set to be equal in compliance withSAEJ2344. The number of batteries stacked in each of the first batteryunit 38F and the second battery unit 38R is twenty-four.

The junction box 36 comprises a main conductor 36 a which electricallyconnects a positive electrode of the first battery unit 38F and theinverter 14, and a sub-conductor 36 b which electrically connects anddisconnects a negative electrode of the second battery unit 38R and theinverter 14.

Further, in the junction box 36, a pre-charge circuit 36 c comprising aresistor 36 d and a pre-charge conductor 36 e connected in series isprovided in parallel with the main conductor 36 a. Opening and closingoperations of the main conductor 36 a, the sub-conductor 36 b, and thepre-charge conductor 36 e are performed in response to opening/closingsignals output from the aforesaid control unit 45. The junction box 36may further comprise a voltage detecting device for detecting an outputvoltage of the battery units 38F, 38R and a current detecting device fordetecting a power current output by the battery units 38F, 38R.

The switch box 35 is located farther from the inverter 14 than thejunction box 36, or in other words in the rearmost part in the space G.

The switch box 35 is interposed between the first battery unit 38F andthe second battery unit 38R as described above. In a physical sensealso, the switch box 35 is preferably located near the midpoint betweenthe first battery unit 38F and the second battery unit 38R so as toshorten the required length of the harness 34. In FIG. 10, the junctionbox 36 is disposed between the battery units 38F, 38R and the electricequipment. In a physical sense also, the junction box 36 is preferablydisposed in front of the switch box 35 so as to shorten the requiredlength of the harness 34.

In contrast, in a vehicle in which the electric equipment is disposed inthe rear of the battery assembly 22, the junction box 36 is preferablydisposed in the rear of the switch box 35.

Referring again to FIG. 3, an opening 22 b is formed in the case 22 aand a floor panel 16 covering the manually-operated relay 35 a fromabove so as to operate the manually-operated relay 35 a in the switchbox 35 from within the passenger compartment 2. Further, a lid 39 isprovided to cover the opening 22 b. The lid 39 is designed to open andclose such that the manually-operated relay 35 a is exposed to thepassenger compartment 2 and hidden therefrom. The switch box 35 islocated between the right and left front seats 32F. By disposing theswitch box 35 in this way, opening and closing the lid 39 and operatingthe manually-operated relay 35 a can be conducted without displacing thefront seat 32F. The switch box 35 may however be disposed in a differentlocation.

Finally, the case 22 a and the battery housing recess 31 will bedescribed in detail.

Referring to FIG. 9, the case 22 a comprises a first battery housingpart P1 for accommodating the first group S1 of the batteries 3, asecond housing part P2 for accommodating the second group S2 of thebatteries 3, and a third housing part P3 for accommodating the thirdgroup S3 of the batteries 3. With respect to the vehicle longitudinaldirection, the second housing part P2 is located to the rear of thefirst battery housing part P1 while the third housing part P3 is locatedto the rear of the second housing part P2.

Referring to FIG. 11, assuming that a height of the first batteryhousing part P1 is h11, a height of the second housing part P2 is h12,and a height of the third housing part P3 is h13, the relationh13>h11>h12 holds.

The battery housing recess 31 is formed by the floor panel 16 and thebattery mounting frame 21 and has a sufficient capacity to accommodatethe groups S1-S3 of the batteries 3. The battery housing recess 31comprises a first recess Q1 formed under the front seat 32F foraccommodating the first group S1 of the batteries 3, a second recess Q2formed under the floor 33 for accommodating the second group S2 of thebatteries 3, and a third recess Q3 formed under the rear seat 32R foraccommodating the third group S3 of the batteries 3.

Assuming that a height of a bottom of the first recess Q1 is h21, aheight of a bottom of the second housing part Q2 is h22, and a height ofa bottom of the third recess Q3 is h23, the relation h23>h21>h22 holds.

The contents of Tokugan 2009-41225, with a filing date of Feb. 24, 2009in Japan, and the contents of Tokugan 2009-166942, with a filing date ofJul. 15, 2009 in Japan, are hereby incorporated by reference.

Although the invention has been described above with reference tocertain embodiments, the invention is not limited to the embodimentsdescribed above. Modifications and variations of the embodimentsdescribed above will occur to those skilled in the art.

For example, the shape of the batteries 3 is not necessarily a flatcuboid. It is not vital that all of the batteries 3 have an identicalshape and identical dimensions.

Although in this embodiment, the two groups S1 and S2 of the batteries 3are provided as the first battery unit 38F, the first vertical unit 38Fmay be constituted by one group of the batteries 3. Also in thisembodiment, the space G is formed above the beam 24 c so that the groupsS1 and S2 of the batteries 3 are located on the right and left of thespace G. However, it is possible to eliminate the space G and arrangethe battery stacks of the first battery unit 38F without a clearance inthe vehicle transverse direction depending on the width W of the lowerpart of the vehicle body and the dimensions of the batteries 3.

The battery mounting frame 21 need not be made in a rectangular shape,and may be made in a different shape depending on the type of thevehicle 1. Instead of connecting the girder 24 w and the beam 24 c in aT-shape, they may be connected in a cruciform shape.

Further, the battery mounting frame 21 is not an essential component ofthis invention. When the batteries 3 are mounted on a vehicle withoutusing the battery mounting frame 21, a preferable weight balance in afront-aft direction of the vehicle is realized by providing a firstbattery unit 38F comprising the vertically stacked batteries 3 and asecond battery unit 38R comprising the transversely stacked batteries 3.

The electric circuit of the battery assembly 22 shown in FIG. 10 is alsonot an essential component of this invention. This invention can beapplied to any vehicle on which a plurality of the batteries 3 aremounted irrespective of the electric circuit of the batteries 3.

INDUSTRIAL FIELD OF APPLICATION

As described above, the vehicle battery mounting structure according tothis invention is preferably applied to an electric vehicle, but notlimited thereto.

The embodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:

The invention claimed is:
 1. A vehicle mounting a plurality of batteries under a floor panel of the vehicle, comprising: a first group of the batteries; a second group of the batteries disposed to the rear of the first group of the batteries with respect to a vehicle longitudinal direction; and a third group of the batteries disposed to the rear of the second group of the batteries with respect to the vehicle longitudinal direction; wherein each of the first group of batteries, the second group of batteries and the third group of batteries has a topmost surface parallel to a road surface that the vehicle is on and not in contact with other batteries or other group of batteries, wherein, when measured from the road surface, a height to the topmost surface of the second group of the batteries is set to be lower than a height to the topmost surface of the first group of the batteries and a height to the topmost surface of the third group of the batteries, and the height to the topmost surface of the third group of the batteries is set to be higher than the height to the topmost surface of the first group of the batteries, and wherein the vehicle comprises a passenger compartment in which a front seat, a rear seat, and a floor located between the front seat and the rear seat are provided, the first group of the batteries is mounted under the front seat, the second group of the batteries is mounted under the floor, and the third group of the batteries is mounted under the rear seat.
 2. The vehicle as defined in claim 1, wherein the second group of the batteries comprises a plurality of the batteries having a direction of stacking in a vertical direction and the third group of the batteries comprises a plurality of the batteries having a direction of stacking in a vehicle transverse direction.
 3. The vehicle as defined in claim 2, wherein the first group of the batteries comprises a plurality of the batteries having a direction of stacking in a vertical direction.
 4. The vehicle as defined in claim 1, further comprising a battery mounting frame in which the first group of the batteries, the second group of the batteries, and the third group of the batteries are fixed in advance as a battery assembly, and the first group of the batteries, the second group of the batteries, and the third group of the batteries are fixed in the vehicle via the battery mounting frame.
 5. The vehicle as defined in claim 4, wherein the battery mounting frame comprises a rectangular frame having a rectangular planar shape and a reinforcing member fixed to an inside of the rectangular frame.
 6. The vehicle as defined in claim 5, wherein the rectangular frame comprises a front edge member disposed at a front end thereof with respect to the vehicle longitudinal direction, and the reinforcing member comprises a girder fixed to the inside of the rectangular frame in a vehicle transverse direction and a beam connecting a girder and the front edge member, the girder and the beam forming a T-shape in a plan view.
 7. The vehicle as defined in claim 5, wherein the vehicle comprises a fixed member for fixing the battery mounting frame.
 8. The vehicle as defined in claim 6, wherein the first group of the batteries and the second group of the batteries are fixed to the rectangular frame in front of the girder with respect to the vehicle longitudinal direction and the third group of the batteries is fixed to the rectangular frame to the rear of the girder with respect to the vehicle longitudinal direction.
 9. The vehicle as defined in claim 4, further comprising a case formed into a predetermined shape and fixed to the battery mounting frame so as to accommodate the first group of the batteries, the second group of the batteries, and the third group of the batteries.
 10. The vehicle as defined in claim 1, wherein the first group of the batteries and the second group of the batteries comprise a space in a center part with respect to a vehicle transverse direction, and the batteries in the first group and the second group comprise terminals projecting into the space.
 11. The vehicle as defined in claim 10, wherein the batteries of the third group comprise terminals projecting frontward with respect to a vehicle longitudinal direction.
 12. The vehicle as defined in claim 10, wherein: the vehicle comprises a front compartment located in front of the passenger compartment with respect to the vehicle longitudinal direction, an electric equipment comprising an electric motor and a related device as a motive force source for traveling is accommodated in the front compartment, and the vehicle further comprises a harness for connecting the terminals of the batteries of the first, second, and third groups, and the electric equipment.
 13. The vehicle as defined in claim 12, wherein the first group of batteries includes a first stack of batteries and a second stack of batteries positioned adjacent to the first stack of batteries in a longitudinal direction of the first stack of batteries, the vehicle including a space between the first stack of batteries and the second stack of batteries, wherein the harness is disposed in the space. 